NUJ freelance organiser John Toner said: “It has been driven by [the union] Unison. I can’t think of any other union that takes the same view.

“We’ve asked them repeatedly to justify it and they never have. Our general secretary has written to Unison a number of times asking them to produce evidence that flash is damaging to anyone with any particular disability, and we’ve never had a response.”

At last year’s disability conference, a compromise was reached by the TUC disability committee which allowed photographers to use low-level flashes.

Photographer Andrew Wiard, who protested outside the conference, said of the latest decision by the disability committee: “This is in clear defiance of TUC policy, in clear defiance of what they were saying last night and in effect is a ban on flash.

“The whole point of photographing a conference is photographing them while they’re in session, not before and afterwards.

“Who is running the TUC?”

A TUC spokesperson said: “The TUC disability conference has decided today that there is to be no use of flash photography during its conference sessions.

“This decision contradicts TUC policy on the use of flash photography at TUC events as agreed by its governing body, the General Council.